1. Field of the Invention
The present invention relates to a steering system for vehicles. Particularly, it relates to a steering system for a vehicle having front and rear wheels, in which the rear wheels as well as the front wheels are steerable by means of a steering wheel.
2. Description of Relevant Art
There have been proposed steering systems for vehicles, such as in Japanese Patent Application No. 56-118698, in which a rear wheel steering sub-system is provided with an off-centered pin directly or indirectly interconnecting left and right rear wheel turning tie rods, which off-centered pin is adapted to rotate by a revolution taken out from a front wheel steering sub-system, to thereby turn rear wheels in the same direction as front wheels and in the opposite direction thereto in accordance with the steering angle of a steering wheel.
In such a steering system for vehicles, the necessary revolution for turning the rear wheels is transmitted from the front wheel steering sub-system through a linkage to a rotatable member on which the off-centered pin is arranged so as to make a crank motion to thereby turn the rear wheels by a desired angle.
With such a steering system, for a vehicle having front and rear wheels, the rear wheels are able to be steered in the same direction as the front wheels for relatively small steering angles of the steering wheel and in the opposite direction thereto for relatively large steering angles thereof.
Accordingly, there is provided favorable vehicle maneuverability when travelling at relatively high speeds, as well as favorable vehicle turning characteristics due to relatively small turning radii possible with large steering angles such as in a U-turn or when steering in and out of a parking space.
However, in such a steering system for vehicles, in which the crank motion of the off-centered pin is converted into a reciprocal motion of the rear wheel turning tie-rods, the steering torque necessary for turning the rear wheels is subjected to a variation such that the steering feeling becomes relatively heavy in the vicinity of the original or neutral position of the rear wheels and, contrary thereto, relatively light near the full-turn position the rear wheels will have each time when turned in the same direction as the the front wheels and in the opposite direction thereto.
The present invention has been achieved to favorably solve such a problem in a conventional steering system for vehicles.